JP2012012582A - Cyclodextrin-containing polyvinyl alcohol gel, and carrier for immobilizing microorganism and wastewater treatment method each using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide cyclodextrin-containing polyvinyl alcohol gel suitable as a carrier for immobilizing microorganisms that simultaneously has an incorporating function of aromatic compounds useful for treatment of aromatic compound-containing wastewater and an excellent adhering function to microorganisms.SOLUTION: The cyclodextrin-containing polyvinyl alcohol gel is obtained by the reaction of polyvinyl alcohol with formaldehyde in the coexistence of cyclodextrin, or is obtained by dispersing a cyclodextrin polymer, which is obtained by the reaction of cyclodextrin with a diisocyanate compound, in polyvinyl alcohol and then by performing a reaction with formaldehyde.

Description

  The present invention relates to a carrier for immobilizing microorganisms for immobilizing microorganisms useful for wastewater treatment, and in particular, a carrier for immobilizing microorganisms useful for treating aromatic compound-containing wastewater, and a wastewater treatment method using the same. It is about.

  Many wastewater discharged from chemical factories contains aromatic compounds such as benzenes and phenols. Wastewater containing such aromatic compounds is often adsorbed with an adsorbent such as activated carbon or biologically treated with an activated sludge method. Thus, the treated wastewater in which the aromatic compound is reduced may be discharged as it is or may be reused as treated water. However, since activated carbon is expensive, it is not used much in the treatment of wastewater discharged in large quantities from large-scale facilities, and must be applied to wastewater treatment from relatively small-scale facilities. Therefore, biological treatment is often performed for wastewater treatment from large-scale facilities. However, since organic compounds such as aromatics are generally difficult to be decomposed and assimilated by biological treatment, the concentration is hardly lowered. Therefore, it takes a long time to treat such wastewater containing aromatic compounds or install a large apparatus, and development of a more rapid and simple wastewater treatment method is desired.

  On the other hand, in order to adsorb and remove organic compounds such as phenols contained in wastewater, for example, Patent Documents 1 to 4 have been proposed as techniques using cyclodextrins having an action function of adsorbing and inclusion of organic compounds. ing. Patent Document 1 discloses a water treatment method for removing malodorous substances such as at least one organic substance, in particular (−) geosmin and (+) 2-methyl-isoborneol, in which water to be treated has a specific structure. In contact with the cyclodextrin having the organic substance to be removed, the purified water is separated from the cyclodextrin. In Patent Document 2, when removing these phenol compounds from a solvent containing 0.1 to 30% by weight of phenol, cresol, or xylenol, β-cyclodextrin is contained as a cyclodextrin monomer, and the cyclodextrin monomer 1 The cyclodextrin polymer obtained by reacting the diisocyanate compound at 6 to 12 moles is brought into contact with the mole. Moreover, in patent document 3, the cyclodextrin polymer obtained by making cyclodextrin and a diisocyanate compound react is mixed with polysaccharide carboxylate aqueous solution, and the liquid mixture by this process is made into halogenated alkaline-earth metal salt aqueous solution. An industrial wastewater containing phenols is treated using a spherical cyclodextrin polymer produced through the dropping step. Patent Document 4 also proposes a method for purifying wastewater using a microorganism-immobilized carrier composed of a material having cyclodextrin bonded to the surface.

JP-T-2001-507618 Japanese Patent No. 4090979 JP 2006-83379 A JP 2001-149975 A

  However, in the method in which cyclodextrin is used as it is or bonded to a carrier as in Patent Document 1, the treatment efficiency is poor because cyclodextrin is easily dissolved in water. On the other hand, in patent document 2 and patent document 3, since cyclodextrin is modified into a water-insoluble polymer, problems such as patent document 1 and patent document 4 can be solved. However, the cyclodextrin polymers of Patent Document 2 and Patent Document 3 have a problem that the amount of microorganisms attached is small because the surface structure is not suitable for the attachment of microorganisms.

  Therefore, the present invention solves the above-mentioned problems, and is a microorganism immobilization carrier having both an aromatic compound uptake action (concentration action) and an excellent microorganism adhesion action, and a high-performance carrier using the same. An object is to provide a wastewater treatment method.

For this purpose, the present invention adopts the following means.
(1) A cyclodextrin-containing polyvinyl alcohol gel obtained by reacting polyvinyl alcohol with formaldehyde in the presence of cyclodextrin, wherein cyclodextrin is present in a covalent bond state in polyvinyl alcohol.
(2) A solution of polyvinyl alcohol and cyclodextrin is gelled by contacting with a solution containing metal ions in the presence of a high molecular polysaccharide and then reacted with formaldehyde. A cyclodextrin-containing polyvinyl alcohol gel in which is present in a covalently bonded state.
(3) A cyclodextrin-containing polyvinyl alcohol gel obtained by dispersing a cyclodextrin polymer obtained by reacting cyclodextrin and a diisocyanate compound in polyvinyl alcohol and then reacting with formaldehyde.
(4) The cyclodextrin-containing polyvinyl alcohol gel according to any one of (1) to (3), wherein the average degree of polymerization of the polyvinyl alcohol is 300 to 30,000.
(5) The cyclodextrin-containing polyvinyl alcohol gel according to any one of (1) to (3), wherein the polyvinyl alcohol has an average degree of polymerization of 500 to 10,000.
(6) A carrier for immobilizing microorganisms comprising the cyclodextrin-containing polyvinyl alcohol gel according to any one of (1) to (5).
(7) A wastewater treatment method for reducing a content of an organic compound in the wastewater by bringing the carrier for immobilizing a microorganism into contact with wastewater containing an organic compound, wherein the carrier for immobilizing a microorganism is (6) A method for treating waste water, which is the carrier for immobilizing microorganisms described above.
(8) The waste water treatment method according to (7), wherein the organic compound is an aromatic compound.
(9) The waste water treatment method according to (8), wherein the aromatic compound is a phenol compound.

  According to the present invention, by introducing cyclodextrin into polyvinyl alcohol by covalent bond, or by dispersing cyclodextrin polymer in polyvinyl alcohol, the organic compound based on the inclusion action inherent in cyclodextrin is obtained. In addition to the uptake (concentration effect) effect, it also has an excellent microbial immobilization function possessed by the formalized polyvinyl alcohol gel, thereby providing a microorganism immobilization carrier having a high wastewater treatment capacity. Moreover, by using the carrier for immobilizing microorganisms of the present invention, wastewater containing organic compounds such as aromatic compounds can be treated efficiently, and a compact wastewater treatment system can be provided. Furthermore, it becomes possible to reduce the excess sludge generated when continuously performing wastewater treatment, and the wastewater treatment method of the present invention is very useful.

1 is a schematic diagram of a CD-containing PVA gel of Embodiment 1. FIG. 3 is a solid ¹³ C-NMR spectrum of the β-CD-containing PVA water-containing gel obtained in Example 1. It is a graph which shows the time-dependent change of the phenol concentration in Test Example 2 (phenol decomposition test). It is the schematic which shows the waste water treatment system of this invention.

(Embodiment 1-1)
The cyclodextrin-containing polyvinyl alcohol gel of the present invention is obtained by reacting polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) with formaldehyde in the presence of cyclodextrin (hereinafter also abbreviated as CD). As a result, as shown in FIG. 1, a CD-containing PVA gel in which CD is introduced into PVA by covalent bonding is obtained.

  The polyvinyl alcohol used in the present invention can be obtained by a known method such as polymerization of a vinyl acetate monomer or saponification of polyvinyl acetate. However, in the case of polymerization, the average degree of polymerization is usually 300 to 30,000. In the range of 500 to 10,000, preferably in the range of 1,000 to 5,000, particularly preferably in the range of 1,000 to 2,000. Is in range. This is because if the average degree of polymerization is excessively large, the solubility in the solvent may be reduced and the content of cyclodextrin may be decreased, and if it is excessively small, a gel having sufficient strength may not be obtained.

  As the cyclodextrin used in the present invention, α-cyclodextrin having 6 glucose units (hereinafter sometimes abbreviated as α-CD), 7 β-cyclodextrin (hereinafter abbreviated as β-CD). And γ-cyclodextrin (hereinafter sometimes abbreviated as γ-CD), etc., among which β-cyclodextrin is preferred. These cyclodextrins can be used alone or in combination of two or more.

  Furthermore, the cyclodextrin may be modified by addition of other functional groups. For example, a cyclodextrin substituted with any of a lower alkyl group having 1 to 4 carbon atoms, a long-chain aliphatic group having 8 to 20 carbon atoms, or a hydroxyalkyl group, a sulfone group, an alkylsulfone group, or the like. Can be mentioned.

  The use amount of the polyvinyl alcohol and cyclodextrin of the present invention is such that the weight ratio (PVA / CD) of cyclodextrin to polyvinyl alcohol is in the range of 0.05 to 20 times, preferably 0.1 to 10 times. More preferably 0.5 to 10 times, particularly preferably 0.5 to 5 times. When the amount of CD used is excessively small, the amount of CD contained in the resulting hydrogel is small, and the amount of organic compounds taken up decreases, resulting in a reduction in wastewater treatment efficiency. Moreover, since the elasticity as a water-containing gel is lost and it becomes weak even if the usage-amount of CD is too large with respect to polyvinyl alcohol, it is preferable to set it as the said range.

  The amount of formaldehyde used in the present invention is usually 0.1 to 20 times (weight ratio), preferably 1 to 20 times, particularly preferably 2 with respect to polyvinyl alcohol (formaldehyde / PVA). .5 to 15 times the amount. If the amount of formaldehyde used is too small, the CD content of the resulting hydrogel is reduced and the cross-linking of PVA is also reduced, so that an effective hydrogel carrier cannot be obtained. Further, even if the amount of formaldehyde used is excessively large, the effect of improving the properties of the water-containing gel reaches its peak and the cost is wasted, so the above range is preferable. In addition, formaldehyde is appropriately selected from an aqueous solution such as formalin and a solid material such as paraformaldehyde.

  The reaction between polyvinyl alcohol and formaldehyde in the presence of cyclodextrin is carried out in a solvent in the presence of an acid catalyst.

  The reaction solvent is not particularly limited as long as it does not participate in the reaction and dissolves the reaction substrate to some extent. For example, water; alcohols such as methanol, ethanol, propanol, and butanol; dimethyl sulfoxide, dimethylformamide, etc. Polar organic solvents; and mixed solvents thereof are used. Among these, water, alcohols, or a water / alcohol mixed solvent is preferable, and water is particularly preferable.

  Examples of the acid catalyst include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, and organic acids such as acetic acid, methanesulfonic acid, benzenesulfonic acid, and toluenesulfonic acid. Among these, sulfuric acid, phosphoric acid, and methanesulfonic acid are preferable, and sulfuric acid is particularly preferable.

  As reaction temperature, it is the range of room temperature-200 degreeC normally, Preferably it is 40-150 degreeC, Especially preferably, it is the range of 40-120 degreeC.

  The reaction time varies depending on the reaction temperature, but is usually in the range of 30 minutes to 24 hours, preferably 1 hour to 12 hours, and particularly preferably 1 hour to 6 hours.

  The cyclodextrin-containing PVA gel thus obtained is molded or molded into a desired shape and used as a carrier for immobilizing microorganisms.

(Embodiment 1-2)
The reaction of polyvinyl alcohol and formaldehyde in the presence of cyclodextrin can be performed in one step as in Embodiment 1-1, but can also be performed in two steps as follows. That is, first, a water-soluble polymer polysaccharide is added to a solution of cyclodextrin and polyvinyl alcohol, and then contacted with a solution containing metal ions to form a gel of a desired shape such as a spherical shape or a rod shape, and then obtained. The gel is reacted with formaldehyde in the same manner as in Embodiment 1-1.

  The water-soluble polymer polysaccharide is a polymer polysaccharide that is water-soluble and has the ability to turn into a water-insoluble or sparingly soluble gel when contacted with metal ions in an aqueous medium. Having a number average molecular weight in the range of from about 5,000 to about 2,000,000, especially from about 5,000 to about 1,500,000. Moreover, what shows the solubility of at least about 10 g / L (25 degreeC) or more normally in the water-soluble state before making it contact with metal ion is used suitably.

  Examples of the water-soluble polymeric polysaccharide having such properties include an alkali metal salt of alginic acid, carrageenan, an alkali metal salt of pectic acid, an alkali metal salt of cellulose glycolic acid, and the like. Among these, an alkali metal salt of alginic acid (preferably a sodium salt) is preferable.

  Examples of metal ions that gel water-soluble polymer polysaccharides include alkali metal ions such as potassium ions and sodium ions, and magnesium ions, calcium ions, strontium ions, barium ions, aluminum ions, cerium ions, and nickel ions. A valent metal ion is mentioned. In the case of an alkali metal salt of alginic acid, magnesium ions and calcium ions are preferable, and calcium ions are more preferable. In the case of carrageenan, potassium ion and sodium ion are preferred.

  The alkali metal ion or polyvalent metal ion concentration at which gelation occurs varies depending on the type of water-soluble polymeric polysaccharide, but is generally 0.01 to 5 mol / L, preferably 0.1 to 1 mol / L. Is within the range. These water-soluble polymer polysaccharides can be used alone or in combination of two or more.

  As a method of bringing a mixture of a solution of cyclodextrin and polyvinyl alcohol and a water-soluble polymer polysaccharide into contact with a solution containing metal ions to form a gel having a desired shape such as a spherical shape or a rod shape, for example, A method in which a mixed solution of cyclodextrin, polyvinyl alcohol and water-soluble polymer polysaccharide is dropped into a solution containing metal ions from the tip; a method in which the mixed solution is dispersed in a granular form using centrifugal force; from the tip of a spray nozzle It can be carried out by a method such as a method of atomizing the mixed solution into a granular form and dropping it. Further, the mixed solution can be poured into the metal ion solution by continuously supplying it as a thin liquid flow from a nozzle opening having a desired hole diameter. The size of the droplet can be freely changed depending on the particle size desired for the final granular fixed product, but in the dropping method, the diameter is usually about 0.1 to about 5 mm, preferably about 0.5 to It is convenient to drop the liquid droplets in the range of about 4 mm, and in the case of the pouring method, the liquid droplets are usually in the range of about 0.5 to 3 cm.

  The gel of the desired shape thus obtained is then reacted with formaldehyde in the same manner as in Embodiment 1-1 to become a cyclodextrin-containing PVA gel that is substantially insoluble in water and has high mechanical strength, and is directly microbial. It can be used as a molded article for body fixation.

(Embodiment 2)
The cyclodextrin-containing PVA gel of the present invention is obtained by dispersing a cyclodextrin polymer in a PVA solution and then reacting with formaldehyde. When obtaining a cyclodextrin-containing PVA composition having a desired shape such as a spherical shape or a rod shape, a water-soluble polymer polysaccharide is added to the PVA solution in which the cyclodextrin polymer is dispersed in the same manner as in the molding method of the first embodiment. It is performed by contacting with a solution containing metal ions to form a desired shape and then reacting with formaldehyde. In addition, reaction with formaldehyde is performed on the same conditions as the case of the cyclodextrin containing PVA gel of Embodiment 1.

  The amount of PVA and cyclodextrin polymer used is usually 0.1 to 30 times the amount of PVA / cyclodextrin polymer (weight ratio), preferably 0.5 to 20 times, and more preferably 1 to 10 times the amount, particularly preferably 1 to 5 times the amount. If the amount of the cyclodextrin polymer used is excessively small, the CD content of the obtained hydrogel is small, and an effective hydrogel carrier may not be obtained. Even if the amount of the cyclodextrin polymer used is excessively large relative to the polyvinyl alcohol, the hydrogel becomes brittle, so the above range is preferable.

  The cyclodextrin polymer is a polymer obtained by reacting cyclodextrin and a diisocyanate compound, and is produced, for example, by the method described in Japanese Patent No. 4090979.

  Examples of the diisocyanate to be used include aromatic, aliphatic and cycloaliphatic diisocyanates which are generally well known and high-functional or high-molecular diisocyanates. Among them, preferred are aromatic diisocyanates and aliphatic diisocyanates, and more preferred are aliphatic diisocyanates. Specifically, 1,5-naphthylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyldimethylmethane diisocyanate, 4,4′-dibenzyl diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene Diisocyanate, 1,4-phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2, 4,4-trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane , 4'-diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, methylcyclohexane diisocyanate and derivatives thereof. Among them, preferably 2,4-tolylene diisocyanate (hereinafter sometimes abbreviated as TDI), 4,4-diphenylmethane diisocyanate (hereinafter sometimes abbreviated as MDI), hexamethylene diisocyanate (hereinafter abbreviated as HDI). May be included). More preferred is hexamethylene diisocyanate.

  The usage-amount of a cyclodextrin and a diisocyanate compound is 3-24 mol of diisocyanate with respect to 1 mol of CD. Preferably, the amount of diisocyanate is 4 to 16 mol, more preferably 6 to 12 mol, and particularly preferably 8 to 10 mol, relative to 1 mol of CD. When the amount of diisocyanate used is less than 3 mol, the yield of cyclodextrin polymer is low, and a strong cyclodextrin polymer that can withstand use may not be obtained.

  The reaction conditions for the cyclodextrin and diisocyanate compound are not particularly limited, and the reaction is performed within a normal range. Specifically, it is about 0.5 to 10 hours in a temperature range of 30 to 150 ° C, preferably 50 to 100 ° C. The reaction can also be performed in a solvent such as dimethylformamide or dimethyl sulfoxide.

  Furthermore, you may add a transition metal compound catalyst and an amine catalyst as needed. Examples of the transition metal compound catalyst include titanium tetrabutoxide, dibutyltin oxide, dibutyltin dilaurate, tin 2-ethylcaproate, zinc naphthenate, cobalt naphthenate, zinc 2-ethylcaproate, molybdenum glycolate, iron chloride, zinc chloride. Etc. Examples of the amine catalyst include triethylamine, tributylamine, triethylenediamine, benzyldibutylamine and the like. Usually, the reaction is preferably carried out in an inert gas atmosphere such as nitrogen or argon, but there is no problem as long as no moisture is mixed in such as a dry air atmosphere or a sealed condition.

  The obtained cyclodextrin polymer may be used as it is, but it is preferable to use it after finely pulverizing it. The particle size obtained by pulverization is preferably 100 μm or less, more preferably 80 μm or less. Although a minimum is not specifically limited, Actually, it is about 1 micrometer.

<Carrier for immobilizing microorganisms>
The cyclodextrin-containing PVA gel of the present invention produced according to Embodiments 1 and 2 is extremely useful as a carrier for immobilizing microorganisms, and organic compounds such as aromatic compounds are brought into the carrier by the inclusion action of cyclodextrin. In addition to being able to be incorporated, the structure based on formalized polyvinyl alcohol is particularly suitable for the attachment of microorganisms and can attach a large amount of microorganisms that decompose organic compounds.

  The microorganisms that can be attached to the carrier are not particularly limited, and any of anaerobic microorganisms and aerobic microorganisms can be used. Examples of microorganisms include, for example, molds such as Aspergillus, Penicillium, and Fusarium; yeasts such as Saccharomyces, Phaffia, and Candida; Escherichia coli, Pseudomonas, Nitrosomonas, Nitrobacter, Paracoccus, Examples include bacteria such as Vibrio, Methanosarcina, and Bacillus. Among these, when treating industrial wastewater, Pseudomonas spp., Acinetobacter spp., Alcigenes spp.

  The carrier for immobilizing microorganisms of the present invention can be used in various facilities for attaching and immobilizing microorganisms by a conventional method and performing wastewater treatment, for example, as shown in FIG. The conditions for use are not particularly limited, and the conventional immobilization carrier can be used as long as it is installed in a state where it can come into contact with drainage. The carrier of the present invention can be used by attaching microorganisms from sludge or the like in advance as carrier curing when performing wastewater treatment.

  The aromatic compound-containing wastewater that can be an object of the present invention is not particularly limited as long as it contains an aromatic compound that can be included by cyclodextrin. For example, phenol, cresol, ethylphenol, isopropylphenol, tert-butylphenol, sec-butylphenol, allylphenol, xylenol, chlorophenol, naphthalene, 2-methylnaphthalene, 2-chloronaphthalene, 1-naphthol, 2-naphthol, acenaphthene, pyrene, sodium pyrenesulfonate, acenaphthene, azulene, 1-cyanonaphthalene, The waste water containing perylene etc. is mentioned. Among them, preferred is waste water containing phenol compounds such as phenol, cresol, ethylphenol, isopropylphenol, tert-butylphenol, sec-butylphenol, allylphenol, xylenol, chlorophenol, and more preferably phenol, cresol, isopropylphenol, xylenol. Wastewater containing water, particularly preferably phenol-containing wastewater.

  Although there is no restriction | limiting in particular as a density | concentration of an aromatic compound containing waste_water | drain, Preferably it is a density | concentration of 10 g / L or less, More preferably, it is a density | concentration of 5 g / L or less. Accordingly, when the concentration of the aromatic compound in the waste water is high, it is appropriately diluted and applied.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to these examples.

Example 1
1-1 Preparation of PVA aqueous solution 8 g of PVA pellets (average polymerization degree 1700, saponification degree 99.8 mol%) are put into 92 g of water and stirred at such a speed that the pellets do not accumulate at the bottom to swell the pellets. It was. The mixture was heated at 80-90 ° C. for about 30-60 minutes until the PVA pellets dissolved. Subsequently, it cooled to 50 degrees C or less under stirring, and prepared PVA aqueous solution.

1-2 Synthesis of β-CD-containing PVA spherical hydrous gel 0.8 g of β-CD powder was dissolved in 10 g of the PVA aqueous solution obtained above, and then 3.3 g of 3 wt% sodium alginate aqueous solution (PVA aqueous solution: 3 wt% alginate) Sodium aqueous solution = 3: 1 (wt / wt)) was added. The obtained solution was dropped onto a 10% aqueous calcium chloride solution using a 10 mL syringe and spheroidized. The obtained spherical gel was immersed in a 10 wt% calcium chloride aqueous solution for about 30 to 60 seconds, and after solid-liquid separation, lightly washed with water. Next, the spherical gel was put into 100 mL of an aqueous solution containing 80 g / L of formaldehyde, 200 g / L of sulfuric acid, and 150 g / L of sodium sulfate, and stirred at 80 ° C. for 3 hours. After cooling, it was separated into solid and liquid, washed with water, and then stirred in 100 mL of 0.5% aqueous sodium hydrogen carbonate solution for one day. After solid-liquid separation, it was washed with water to obtain a β-CD-containing PVA water-containing gel. The solid ¹³ C-NMR spectrum of the β-CD-containing PVA water-containing gel obtained in Example 1 is shown in FIG. Thereby, the introduction of β-CD into the PVA gel can be confirmed.

(Examples 2-36)
As shown in Table 1, a β-CD-containing PVA hydrogel was synthesized according to Example 1 by changing the β-CD usage rate, the formaldehyde usage rate, and the reaction temperature.

(Comparative Example 1)
To 10 g of the PVA aqueous solution obtained in Example 1-1, 3.3 g of a 3 wt% sodium alginate aqueous solution (PVA aqueous solution: 3 wt% sodium alginate aqueous solution = 3: 1 (wt / wt)) was added. The solution was dropped from a syringe onto a 10% calcium chloride aqueous solution and spheroidized. The spherical gel was immersed in a 10 wt% calcium chloride aqueous solution for about 30 to 60 seconds, and after solid-liquid separation, lightly washed with water. Next, the obtained spherical gel was put into 100 mL of an aqueous solution containing 80 g / L of formaldehyde, 200 g / L of sulfuric acid, and 150 g / L of sodium sulfate, and kept at 80 ° C. for 90 minutes with stirring. After solid-liquid separation, it was washed with water, and then stirred in 100 mL of 0.5% aqueous sodium hydrogen carbonate solution for one day. After solid-liquid separation, it was washed with water to obtain a spherical PVA water-containing gel.

(Comparative Example 2)
A trade name “Kragale” (Kuraray Co., Ltd.) marketed as a carrier for immobilizing microorganisms was used as Comparative Example 2. Kragale is a PVA spherical gel obtained by reacting PVA with formaldehyde.

Table 1 shows the measurement results of specific gravity and Young's modulus of each of the above Examples and Comparative Examples.

(Example 37)
37-1 Synthesis of CD polymer A 500 mL three-necked flask equipped with a reflux condenser and a dropping funnel was charged with 20.0 g (0.018 mol) of β-CD, 10 drops of di-n-butyltin dilaurate, and 150 mL of dimethylformamide (DMF). And dissolved with stirring. After sufficiently replacing the nitrogen in the flask, a DMF (50 mL) solution containing 29.6 g (0.18 mol) of hexamethylene diisocyanate (HDI) was slowly added dropwise, followed by stirring at 70 ° C. for 24 hours. As soon as the reaction progressed, a white polymer precipitated. The reaction product was poured into chloroform and stirred for 3 hours, and then the residue was suction filtered and dried in vacuo at 60 ° C. to obtain a CD polymer. The β-CD polymer was pulverized to 75 μm or less with a ball mill to form a powder.

37-2 Synthesis of CD-containing PVA gel composition 10 g of PVA aqueous solution prepared in the same manner as in Example 1-1 was mixed with 0.16 g of the powdered CD polymer obtained above, and then 3 wt% aqueous sodium alginate solution. 3.3 g (PVA aqueous solution: 3 wt% sodium alginate aqueous solution = 3: 1 (wt / wt)) was added. The obtained suspension was dropped onto a 10% aqueous calcium chloride solution using a 10 mL syringe and spheroidized. The obtained spheroidized gel was immersed in a 10 wt% calcium chloride aqueous solution for about 30 to 60 seconds, and after solid-liquid separation, lightly washed with water. Next, the spherical gel was put into 100 mL of an aqueous solution containing 80 g / L of formaldehyde, 200 g / L of sulfuric acid, and 150 g / L of sodium sulfate, and stirred at 80 ° C. for 3 hours. After cooling, it was separated into solid and liquid, washed with water, and then stirred in 100 mL of 0.5% aqueous sodium hydrogen carbonate solution for one day. After solid-liquid separation, it was washed with water to obtain a β-CD-containing PVA water-containing gel composition.

(Example 38)
A β-CD-containing PVA water-containing gel composition was obtained in the same manner as in Example 37-2 except that 0.48 g of the powdered CD polymer obtained in Example 37-1 was used.

(Examples 39-40)
The powdery CD polymer obtained in Example 37-1 was used in the same manner as in Example 37-2 using 0.64 g (Example 39) and 0.80 g (Example 40). A contained PVA water-containing gel composition was obtained.

<Test 1> Phenol uptake test 1.0 g of the carriers of Examples and Comparative Examples obtained above and 5 mL of an aqueous phenol solution (phenol concentration 500 mg / L) were placed in a 50 mL Erlenmeyer flask and heated to 25 ° C. using a Unithermo shaker. And shaken at 80 rpm. After 2 hours or 24 hours, the carrier and the solution were separated by suction filtration, and the phenol concentration in the solution was measured by gas chromatography. The results are shown in Table 2.

  From Table 2, the β-CD-containing PVA water-containing gel of the present invention showed a high phenol uptake effect based on the inclusion action of cyclodextrin.

<Test 2> Phenol Compound Decomposition Test 2-1 Immobilization of Microorganism 50 g of each of the carriers obtained in Example 1, Comparative Example 1 and Comparative Example 2 obtained above was added to 500 mL of a phenol-degrading bacterial medium (medium composition: 1 L of water). K ₂ HPO ₄ 10.49 g, KH ₂ PO ₄ 5.44 g, MgSO ₄ · 7H ₂ O 0.05 g, MnSO ₄ · 4H ₂ O 5.0 mg, CaCl ₂ · 2H ₂ O 0.662 mg, FeSO ₄ · 7H ₂ O 0. 125 mg, L-tryptophan 30 mg, (consisting of (NH ₄ ) ₂ SO ₄ 2.00 g and 7.21 g glucose as a carbon source, 0.5 g casamino acid, 0.5 g phenol) and 100 mL distilled water in an Erlenmeyer flask, Sterilized in an autoclave (121 ° C, 20 minutes) After sterilization, inoculated with phenol-degrading bacteria and aerated at room temperature for 1 month Culturing, phenol-degrading bacteria to adhere to the carrier immobilizing microorganisms (adhesion) to obtain a carrier. Phenol degrading bacteria were used DC1002CG Novo Jai arm Japan Co. provided.

2-2 Degradation test of phenolic compound Immobilization (adhesion) of phenol-degrading bacteria obtained in 2-1 each was 500 mL of medium (medium composition: 10.49 g of K ₂ HPO ₄ for 1 L of water, KH ₂ PO ₄ 5 .44 g, MgSO ₄ · 7H ₂ O 0.05 g, MnSO ₄ · 4H ₂ O 5.0 mg, CaCl ₂ · 2H ₂ O 0.662 mg, FeSO ₄ · 7H ₂ O 0.125 mg, L-tryptophan 30 mg, ((NH ₄ ) ₂ 1 mL of SO ₄ and 500 mg of phenol as a carbon source), and cultured at room temperature under aeration.1 mL of the culture solution was collected with a syringe every predetermined time and sterilized with a pretreatment disk The sample solution was measured with a gas chromatograph and the residual phenol concentration was followed.

  The results of the phenol degradation test are shown in FIG. From the results shown in FIG. 3, the phenol-degrading bacterium-immobilized (adherent) carrier comprising the β-CD-containing PVA water-containing gel of the present invention (Example 1) showed an excellent phenol degrading action, and after 48 hours, the phenol residual concentration was 37 ppb, After 60 hours, it was below the detection limit. On the other hand, when the carriers of Comparative Examples 1 and 2 were used, 50% or more of phenol remained even after 60 hours.

<Test 3> Comparison of the amount of phenol-degrading bacteria-immobilized carrier 3-1 Extraction of bacterial cell DNA 0.1 g of phenol-degrading bacteria-immobilized (attached) carrier obtained in Test Example 2-1 was weighed and marketed. Using the DNA extraction kit (ISOILfor Beads Beating), bacterial cell DNA was extracted according to the protocol.

3-2 Amplification of Bacterial DNA In the presence of primers (518R and 314F-GC) for amplifying the 16rRNA gene and dNTP as a DNA raw material, using the bacterial cell DNA obtained in Test Example 3-1. PCR reaction was performed using ExTaq DNA polymerase manufactured by Takara Bio Inc. The PCR conditions were set as follows.
Step 1: (95 ° C., 3 minutes) × 1 cycle Step 2: (94 ° C., 1 minute, 55 ° C., 1 minute, 72 ° C., 3 minutes) × 24 cycles Step 3: (72 ° C., 10 minutes) × 1 cycle

3-3 Comparison of the amount of bacterial cells The DNA obtained in Comparative Test Example 3-2 was subjected to electrophoresis using a 1.8% agarose gel. Subsequently, the gel was immersed in an ethidium bromide solution having a concentration of 2 μg / ml to bind the ethidium bromide to DNA. Ethidium bromide was excited using a DNA imaging apparatus (LAS-3000 manufactured by FujiFilm) to detect red fluorescence of DNA. The amount of attached cells was compared from the concentration of the 16 rRNA gene band based on phenol-degrading bacteria.

  The measurement results of the amount of cells are shown in Table 3. As shown in the results of Table 3, it was found that the β-CD-containing PVA gel of the present invention can attach 1.8 times the amount of cells compared to the carrier of Comparative Example 2.

<Test 4> Comparison of floating sludge amount Using the carriers of Examples 22, 17, 31, and 36 and Comparative Examples 1 and 2, a phenol degradation test was conducted in the same manner as in Test 2, and the amount of floating sludge (MLSS) at that time ). The amount of suspended sludge was measured according to the sewage test method by sampling the culture solution (suspension) over time from the reactor. Table 4 shows the amount of suspended sludge over time in each example.

From Table 4, it was found that by using a carrier comprising the CD-containing PVA gel of the present invention, the generation of floating sludge can be reduced from 1/2 to 1/3. The reduction in the generation of floating sludge leads to a reduction in excess sludge, which is a very significant advantage in wastewater treatment.

Claims (9)

  A cyclodextrin-containing polyvinyl alcohol gel obtained by reacting polyvinyl alcohol with formaldehyde in the presence of cyclodextrin, wherein cyclodextrin is present in a covalent bond state in polyvinyl alcohol.   A solution of polyvinyl alcohol and cyclodextrin is gelled by contacting with a solution containing metal ions in the presence of a high molecular weight polysaccharide, and then reacting with formaldehyde. The cyclodextrin is covalently bonded to polyvinyl alcohol. A cyclodextrin-containing polyvinyl alcohol gel present in a state.   A cyclodextrin-containing polyvinyl alcohol gel obtained by dispersing a cyclodextrin polymer obtained by reacting cyclodextrin and a diisocyanate compound in polyvinyl alcohol and then reacting with formaldehyde.   The cyclodextrin-containing polyvinyl alcohol gel according to any one of claims 1 to 3, wherein the average degree of polymerization of the polyvinyl alcohol is 300 to 30,000.   The cyclodextrin-containing polyvinyl alcohol gel according to any one of claims 1 to 3, wherein the polyvinyl alcohol has an average degree of polymerization of 500 to 10,000.   A carrier for immobilizing microorganisms, comprising the cyclodextrin-containing polyvinyl alcohol gel according to any one of claims 1 to 5. A wastewater treatment method for reducing the organic compound content in the wastewater by bringing a carrier for immobilizing microorganisms into contact with wastewater containing an organic compound,
The method for wastewater treatment, wherein the microorganism-immobilizing carrier is the microorganism-immobilizing carrier according to claim 6.   The wastewater treatment method according to claim 7, wherein the organic compound is an aromatic compound. The waste water treatment method according to claim 8, wherein the aromatic compound is a phenol compound.

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